Multi-box raiding if you do it right is a lot of upkeep. Flasks, Enchants, Gems, Respecs with talent changes, Repairs, Professions etc... Their casualclysm model it would not surprise me if they made the fights more tank and spank with less aoe and a few more gimmicks.
I keep having the urge to 10 box and when I get close something else takes ahold of my time/focus. Right now I'm running the 4 shams in ICC10 with some RL friends and a couple guildies. To me that is probably the samething that I will do with Cata.